Injection molded branched polyesters

ABSTRACT

Polyester moulding materials which can be injection moulded on a technical scale to give products having good mechanical properties are obtained by having present in the polyesterification mixture, besides a terephthalic or mainly terephthalic acid component and a diol component, 0.05-3 moles percent, on the acid component, of a compound containing at least 3, preferably 3 or 4, ester-forming groups this may for example be a tri- or tetra-carboxylic acid, a triol or tetrol, or a hydroxy carboxylic acid containing in all 3 or more ester-forming groups.

United States Patent Rich et al.

[ 51 Sept. 19, 1972 INJECTION MOLDED BRANCHED POLYESTERS [72] Inventors:Rene Rich; Yves Vaginay, both of Lyon, France abandoned.

[52] U.S. Cl. ..260/75 T, 260/75 R, 264/328 [51] Int. Cl. ..C08q 17/04[58] Field of Search ..264/328; 260/75 [56] References Cited UNITEDSTATES PATENTS 2,895,946 [[1959 Huffman ..260/75 3,048,565 8/1962 Gallet a]. ..260/75 3,227,680 l/l966 Tamblyn et a1 ..260/47 3,251,809 5/1966Lockwood et a]. ..260/75 3,361,848 1/1968 Siggel et a1. ..260/8733,504,080 3/1970 Siggel et a1. ..264/235 3,516,957 6/1970 Gray et a1...260/22 FOREIGN PATENTS OR APPLICATIONS 6,5 15,106 2/1967 NetherlandsPrimary Examiner-Melvin Goldstein Attorney-Cushman, Darby & Cushman [57]ABSTRACT Polyester moulding materials which can be injection moulded ona technical scale to give products having good mechanical properties areobtained by having present in the polyesterification mixture, besides aterephthalic or mainly terephthalic acid component 4 Claims, No DrawingsINJECTION MOLDED BRANCHED POLYESTERS This is a division of our copendingapplication, Ser. No. 717,415, filed Mar. 29, 1968 and now abandoned.

Polyester moulding materials which can be injection moulded on atechnical scale to give products having good mechanical properties areobtained by having present in the poly-esterification mixture, besides aterephthalic or mainly terephthalic acid component and a diol component,0.05-3 moles percent, on the acid component, of a compound containing atleast 3, preferably 3 or 4, ester-forming groups; this may for examplebe a trior tetra-carboxylic acid, a trio] or tetrol, or a hydroxycarboxylic acid containing in all 3 or more ester-formin g groups.

When polymers which may exist in amorphous, crystalline and intermediateforms, such as polyesters for example, are employed for moulding, it isoften desirable for the polymer in the moulded object to have a highdegree of crystallinity, because the mechanical properties of acrystallized product are generally better than those of the same productin the amorphous state. Moreover, mould release of a crystallizedarticle generally takes place -more readily than with an amorphousarticle.

In addition, it is difficult to employ a shaped object obtained fromsuch polymers in the amorphous state, because subsequent crystallizationmay occur under the action of various stresses of a mechanical, chemicalor thermal nature. Such crystallization generally occurs heterogeneouslyand brings about local variations in properties, which set up internalstresses detrimental to the properties of the object as a whole.

By reason of these phenomena, ethylene polyterephthalate, although easyto bring into the form of filaments or films, is used for moulding onlywith difficulty. For this latter application, a certain number ofconditions must be observed. Thus it is necessary: (1) To effectnucleation, which permits of reducing the induction period forcrystallization and in addition prevents the formation of largecrystallites which are responsible for subsequent fragility of themoulded articles, (2) To operate in a fairly strongly heated mould, thesecond order transition point of the polyester being about 80 C. and therate of crystallization becoming appreciable only at about 140 C., and(3) To plasticize the polymer with the object of accelerating thecrystallization in order to obtain acceptable moulding rates.

Despite these precautions, it remains difficult to mould complicatedarticles correctly and the residence time in the mould has to be long,more than one minute.

These disadvantages may be avoided by employing polyesters derived fromterephthalic acid and from diols containing more than two carbon atoms,because the second order transition points of these polymers are low andtheir rate of crystallization high at moderate temperatures.

Of these polymers, trimethylene, tetramethylene and hexarnethylenepolyterephthalate are particularly interesting by reason of the readyavailability of the starting materials. However these polymers givemoulded articles whose shock resistance is insufiicient for manyapplications.

It is an object of the present invention to provide moulding materialswhich can readily be shaped in the molten state and which also givemoulded objects having good mechanical properties.

The moulding materials of the invention comprise essentially a polyesterof specific viscosity (measured at 25 C. on a 1 percent by weightsolution in orthochlorophenol) above 0.5, the acid component of the saidpolyester being essentially aromatic and at least mole percent thereofbeing terephthalic'acid, and the diol component being essentially apolymethylene diol with three to 10 carbon atoms in the molecule, thepolyester comprising also units providing cross-linking sites andderived from 0.05-3 mole percent, reckoned on the acid, of at least onecompound having at least 3 ester-forming groups.

The invention includes also the moulding of these materials in themolten state, and moulded objects ob tained thereby. Those objects havehigh shock resistance and high rigidity.

It will be understood that the term acid component as employed hereindoes not include within its scope the compound providing cross-linkingsites even when this contains an acid group or groups. When the acidcompound comprises less than percent of terephthalic acid, the remaindermay be for example isophthalic acid, p,p'-dicarboxydiphenylmethane oranother aromatic dicarboxylic acid.

The diols from which the polyesters are obtained are of the formulaOH(CI-I ),,OH, n being an integer from three to 10 inclusive. Thepreferred polyesters are prepared from trimethylene-, tetramethyleneorhexamethylene-glycol.

The polyfunctional compounds which may be employed in accordance withthe invention preferably contain three or four ester-forming groups.There may be mentioned more particularly tricarboxylic acids, such astrimesic acid, and tetracarboxylic acids, such as pyromellic acid, andtheir derivatives, triols, such as trimethylolpropane, tetrols, suchaspentaerythritol, dihydroxy carboxylic acids and hydroxy dicarboxylicacids.

The proportion of compound comprising at least three groups capable offorming ester linkages is between 0.05 and 3 moles per hundred moles ofdiacid constituent (i.e. mole percent). In the case of trifunctionalcompounds, quantities between 0.1 and 2.5 mole percent are preferablyemployed, and in the case of tetrafunctional compounds from 0.1 to 1mole percent. Compounds containing more than four reactive functions,although they may be employed in accordance with the invention, are moredifficult to use.

If more than 3 mole percent of trior polyfunctional compound is used theproducts obtained can in practice be shaped only in solution and usedonly as coatings or coverings.

The polyester component is preferably prepared from a lower alkyl esterof terephthalic acid and more particularly from dimethyl terephthalate.Ester interchange is effected between this ester and the diol, in thepresence of the compound comprising more than two ester-forming groups,Whereafter the product is subjected to polycondensation. The esterinterchange and polycondensation reactions are carried out by processesand in the presence of catalysts known per The mouldable materials ofthe invention may contain organic fillers, such as phenolphthalein orcrystalline polymers of high melting point, or mineral fillers such astitanium dioxide, silica, carbon black or magnesium silicate. Thesesubstances, provided they are finely divided and homogeneouslydistributed in the polymer, favor regular crystallization in the form ofspherulites of small dimensions, which further improves the shockresistance of the moulded articles. 5 Fibrous fillers may also beemployed, for example organic synthetic fibers, metal fibers or glassfibers.

The moulding materials of the invention are shaped in the molten state;they are particularly suited to injection moulding, permitting very highmoulding rates with unheated moulds.

The moulded objects of the invention have excellent mechanicalproperties, especially high shock resistance and high rigidity. Theseproperties are only very slightly affected by conditions of moisture andare much less modified by a rise in temperature than those of ethylenepolyterephthalate.

The invention illustrated in the following examples, which are given byway of indication and have no limiting character.

In these examples, the specific viscosity of the polymers is measured at25 C. on a 1 percent by weight solution in ortho-chlorophenol, and themelt viscosity is determined at 285 C. in accordance with the ASTMDstandard 123 8-62T, condition K. Parts are by weight.

EXAMPLE 1 Into a stainless steel reactor heated by passing a mixture ofdiphenyl and phenyl oxide through a jacket, and provided with a stirrer,an evacuating device and the usual control and regulating means, aresimultaneously charged in the cold:

22.7 moles ofdimethyl terephthalate 440 parts 28.7 moles ofbutane-1,4-diol 259 parts 0.02 mole of dimethyl hydroxy 0.475 partterephthalate 0.01 mole of butyl ortho-titanate 0.484 part.

Specific viscosity Melt viscosity EXAMPLE 2 Into the stainless steelreactor are simultaneously charged:

22.7 moles ofdimethyl terephthalate 440 parts 28.7 moles ofbutane-l,4-diol 259 parts 0.05 mole of trimethyl trimesate 1.145 parts0.0l mole of butyl ortho-titanate 0484 part.

The ester interchange commences at about C. 65

After heating for 2 hours, the temperature of the mass reaches 250 C.and the theoretical quantity of methanol has distilled off. The pressureis then brought to 2,600 baryes in 1 hour 10 minutes. Afterpolycondensation for 1 hour further at 265 C., the polymer is cast.

Its properties are:

Specific viscosity Melt viscosity EXAMPLE 3 into the stainless steelreactor are simultaneously charged:

15 moles of dimethyl terephthalate 291 parts 19 moles of butane-1,4-diol171 parts 0.02 mole of pentaerythritol 0.306 part 0.009 0.009 mole ofbutyl oitho-titanate 0.32 part.

The ester interchange commences at about C.; after about 1 hour 55minutes, the theoretical quantity of methanol has distilled ofi and thetemperature of the mass reaches 250 C. The pressure is gradually broughtto 2,600 baryes in 1 hour 10 minutes. After polycondensation for 55minutes at 265 C., the polymer is cast.

Its properties are: Specific viscosity Melt viscosity EXAMPLE 4 Into thestainless steel reactor are simultaneously charged:

15 moles of dimethyl terephthalate 291 parts 19 moles of butane-1,4-diol171 parts 0.06 mole of trimethylolpropane 0.804 part 0.009 mole of butylortho-titanate 0.32 part.

Specific viscosity Melt viscosity EXAMPLE 5 There are introduced into astainless steel agitated autoclave provided with control and regulatingdevices:

20 moles of dimethyl terephthalate 3,880 parts 25 moles ofbutane-1,4-diol 2,250 parts 0.05 mole of pentaerythritol 6.8 partslitharge 7 parts Sb O 2.3 parts.

The ester interchange commences at C. and lasts 2 hours 10 minutes.

The pressure is then gradually reduced over two hours to 2,600 baryes,the temperature reaching 260 C. The polycondensation is continued for 1hour 20 minutes, and the polymer is cast, at 262 C.

Its properties are:

Specific viscosity 1.12 Melt viscosity 2200 P0.

EXAMPLE 6 Into a stainless steel reactor as in Example 1 aresimultaneously charged:

14 moles of dimethyl terephthalate 271 parts 18 moles of hexane-1,6-diol212 parts 0.1 1 mole of trimethylolpropane 1.5 part 0.009 mole of butylortho-titanate 0.3 part.

The ester interchange commences at about 145 C. and ends at about250 C.A vacuum of 800 baryes is gradually applied over 1 hour 5 minutes. Afterpolycondensation for 1 hour 3 minutes, a temperature of 275 C. isreached and the polymer is cast.

Its properties are:

Specific viscosity 1.09 Melt viscosity 420 Po.

The polymers of the preceding Examples, and control polymers preparedunder the same conditions but without the polyfunctional compound, weremoulded in a screw-type press, DK 60 brand, into notched shock testpieces measuring 4 X 6 X 60 mm.

2 seconds Total duration of the cycle/22 seconds One hundred test piecesof each batch were moulded. Immediately before the tests, all the testpieces were heated at 140C. for 1 hour, this heating having the objectof creating an artificial aging in order to eliminate any difierenceswhich may exist between the first and last moulded batches. These testpieces were examined in accordance with the' DIN standard No. 53,453. I

The results are given in Table I.

m hexamethylene polyterephthalate m, tetramethylene polyterephthalateThese measurements were made with a Charpy striker carried on a pendulum(ZWICK brand) of 5 kgcm., at 25 C., hydgrometric state 0 Under identicalworking conditions, parallelpipedic test pieces measuring 4 X 6 X 60mm., based upon tetramethylene polyterephthalate with or withouttrifunctional linkages, were moulded.

These test pieces were subjected to a test identical to that describedin the DIN standard 53,452, except that the two supports were 48 mmapart, which gives for the ratio La/h a value of 12 instead of 10 inthestandard.

All the measurements were made at 25 C., hydgrometric state I 0, on ahorizontal AMSLER dynamometer 200 kg., type 02 ZH 1 18.

The following values were obtained:

TABLE 11 Proportion of Specific Maximum trifunctional viscosity theexternal fibers deflection compound (kg/mm) mm.

These values show that polymers according to this application have highrigidity combined with high shock resistance.

EXAMPLE 7 A polymer based upon terephthalic acid and butanel,4-diolcontaining 2 trifunctional linkages to 1,000 units is obtained under theconditions described in Example 2 and is brought into the form ofparallelepipedic granules measuring 4 X 4' X 2 mm.

These granules are disposed in an enclosed space heated at 220 C. undera pressure of 250 baryes for 5 hours. Stirring is effected by means of acentral helical stirrer. The specific viscosity changes from 1.32 to1.87 in the course of the operation.

EXAMPLE 8 A polymer based upon terephthalic acid and butanediolcontaining 6 trifunctional linkages to 1,000 units is prepared underconditions similar to those of Examples 1, 2 and 4, and is brought intothe form of granules measuring 4 X 4 X 2 mm.

These granules are disposed in an enclosed space heated at 220 C., andthe latter is purged with nitrogen under atmospheric pressure at a rateof flow of 15 liters per minute. The nitrogen has previously been freedfrom any trace of oxygen and moisture and preheated to 220 C.

The operation lasts 5 hours and the specific viscosity of the polymerchanges from 1.09 to l .79.

As before, postcondensed non-modified polymers, and modified polymers,also postcondensed, are moulded in a screw-type press, brand DK 60, inthe form of notched shock test pieces measuring 4 X 6 X 60 mm. in orderto compare the impact strength (DIN standard No. 53,453).

The moulding conditions are:

Duration of the cycle 25 seconds One hundred test pieces of each batchwere placed on a CHARPY striker carried on a pendulum, ZWlCK brand, ofkg/cm., after having previously been heated for 1 hour at 140 C.

Other test pieces were subjected to the test derived from the DINstandard 53,452 described in the preceding examples. The followingresults were obtained:

Comparison of the results set out in this Table with those of Table Iand Table II show:

1. That it is possible according to the invention to obtain the sameshock resistance in an unmodified polymer postcondensed for 5 hours inthe solid state, and

2. That, for an identical postcondensation, the shock resistance of thepolymers of the invention is much greater than that of an unmodifiedpolymer.

We claim:

1. A molded article having a basis of a polyester and obtained byinjection molding a material consisting essentially of a polyester ofspecific viscosity (measured at 25 C on a 1 percent by weight solutionin ochlorophenol) above 0.5, the acid component of the ester structuralunits of said polyester being essentially aromatic and comprising -100mol percent of terephthalic acid, and the diol component of at least 97percent of such units being a polymethylene diol having three to 10carbon atoms in the molecule, which polyester contains also, as the onlyadditional structural units, 0.05 to 3 mol percent of structural unitsbeing derived from a tricarboxylic acid, a tetracarboxylic acid, atriol, a tetrol, a dihydroxycarboxylic acid or a hydroxydicarboxylicacid which units provide branching and cross-linking points.

2. A molded article according to claim 1, in which the diol component isselected from trimethylene glycol, tetramethylene glycol, andhexamethylene glycol, and the additional structural units are derivedfrom trimesic acid, pyromellitic acid, trimethylolpropane,pentaerythritol or hydroxyterephthalic acid.

3. A molded article according to claim 1 in which the polyester contains0.1 to 2.5 mol percent of said additional structural units.

4. A molded article according to claim 2, in which the polyestercontains 0.1 to 1 mol percent of said addition structural units.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,692,7Mt I DATED I September 19, 1972 INVENT0R(5) 1 RENE PICH and YVESVAGINAY It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

On the front page format, change the first inventore name "Rich" to--Pich--.

Signed and Sealed this second Day of March 1976 [SEAL] Attest:

RUTH C. MA SON C. MARSHALL DANN Attestmg Officer Commissioner oflarenrsand Trademarks

2. A molded article according to claim 1, in which the diol component isselected from trimethylene glycol, tetramethylene glycol, andhexamethylene glycol, and the additional structural units are derivedfrom trimesic acid, pyromellitic acid, trimethylolpropane,pentaerythritol or hydroxyterephthalic acid.
 3. A molded articleaccording to claim 1 in which the polyester contains 0.1 to 2.5 molpercent of said additional structural units.
 4. A molded articleaccording to claim 2, in which the polyester contains 0.1 to 1 molpercent of said addition structural units.